package com.zach.util;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
 * 安全相关工具类
 * @author Administrator
 *
 */
public class SecurityUtil {
	private static Log log = LogFactory.getLog(SecurityUtil.class);
	/**
	 * 字符串MD5加密
	 * 
	 * @param s
	 * @return
	 */
	public static String stringToMD5(String str) {
		try {
			byte[] strTemp = str.getBytes();
			MessageDigest mdTemp = MessageDigest.getInstance("MD5");
			mdTemp.update(strTemp);
			return toHexString(mdTemp.digest());
		} catch (Exception e) {
			log.error("获取加密方法时出现异常，不能加密 ！");
			return str;
		}
	}

	/**
	 * 根据文件名获得文件的MD5值
	 * 
	 * @param fileName 代表一个文件
	 * @return 加密后的文件
	 */
	public static String fileNameToMD5(String fileName) {
		InputStream inputStream = null;
		try {
			inputStream = new FileInputStream(fileName);
			return streamToMD5(inputStream);
		} catch (Exception e) {
			log.error(e.getMessage()+" 加密文件失败!");
			e.printStackTrace();
			return null;
		} finally {
			if (inputStream != null) {
				try {
					inputStream.close();
				} catch (IOException e) {
					log.warn(e.getMessage()+" 关闭文件流时失败！");
					e.printStackTrace();
				}
			}
		}
	}

	/**
	 * 根据输入流获得文件MD5值 
	 * 
	 * @param inputStream
	 * @return
	 */
	public static String streamToMD5(InputStream inputStream) {
		try {
			MessageDigest mdTemp = MessageDigest.getInstance("MD5");
			byte[] buffer = new byte[1024];
			int numRead = 0;
			while ((numRead = inputStream.read(buffer)) > 0) {
				mdTemp.update(buffer, 0, numRead);
			}
			return toHexString(mdTemp.digest());
		} catch (Exception e) {
			return null;
		}
	}

	private static String toHexString(byte[] md) {
		char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
		int j = md.length;
		char str[] = new char[j * 2];
		for (int i = 0; i < j; i++) {
			byte byte0 = md[i];
			str[2 * i] = hexDigits[byte0 >>> 4 & 0xf];
			str[i * 2 + 1] = hexDigits[byte0 & 0xf];
		}
		return new String(str);
	}
}
